Cooling device for engine

ABSTRACT

An engine cooling device is provided, which uses a fewer number of ducts for coolant circulation to reduce cost and weight and to make the duct layout easy, and which improves the durability of a differential pressure valve. In the engine cooling device in which a coolant is circulated by a water pump  4  through a coolant circulation flow path  9  at least including a heater circulation flow path  7  that circulates the coolant between a cooling jacket  1  provided at least to one of a cylinder head and a cylinder block of the engine and a heater core  6 , a bypass flow path  8  that communicates the cooling jacket  1  with a portion of the heater circulation flow path  7  downstream of the heater core  6  is provided, and a differential pressure valve  11  that opens when fluid pressure on the side of the cooling jacket  1  exceeds a predetermined value is disposed at a point of exit of the coolant from the cooling jacket  1  to the bypass flow path  8.

TECHNICAL FIELD

The present invention relates to an engine cooling device, and more particularly to an engine cooling device having a heater circulation flow path for circulating a coolant through a heater core, and a bypass flow path that bypasses the heater core.

BACKGROUND ART

An engine cooling device is configured to include a coolant circulation flow path having a cooling jacket provided to the engine, a radiator, and a water pump so that the coolant heated to a high temperature after the heat exchange at the cooling jacket is passed through the radiator and cooled down, before being returned to the cooling jacket by the water pump. The coolant circulation flow path is typically provided with a bypass flow path that bypasses the radiator and returns the coolant to the cooling jacket during warm-up of the engine. A known cooling device is provided with a thermostat device upstream of the water pump in the direction of coolant flow in order to distribute the coolant adequately to the main circulation flow path passing through the radiator and the bypass flow path of the coolant circulation flow path in accordance with the coolant temperature (see, for example, Patent Literature 1).

In another known configuration for an engine cooling device, a heater circulation flow path is provided for circulating part of the coolant from the cooling jacket through a heater core for a vehicle interior air-conditioning device. In addition, in order to control the flow of coolant to the main circulation flow path passing through the radiator, the heater circulation flow path, and the bypass flow path, an open/close valve is disposed in the bypass flow path together with a thermostat device, which is opened when the coolant temperature is high and closed when the temperature is low (see, for example, Patent Literature 2).

In the configuration of Patent Literature 2, when the coolant temperature is low, the thermostat device closes off the main circulation flow path that passes through the radiator and the open/close valve closes off the bypass flow path, too, so that coolant flows only through the heater circulation flow path. In this state, if the engine rpm is increased, the coolant pressure will be increased, which may cause trouble. Accordingly, there has been known a configuration in which the thermostat device is provided with a function of a differential pressure valve, i.e., of opening when coolant pressure exceeds a preset level, and a bypass flow path is provided that bypasses the heater circulation flow path at a position between the cooling jacket and radiator of the main circulation flow path, with a control valve (differential pressure valve) that opens when the pressure exceeds a value lower than the above preset pressure of the thermostat device being provided in the bypass flow path (see, for example, Patent Literature 3).

In another known configuration, as shown in FIG. 4, there are provided a main circulation flow path 25 connecting the cooling jacket 21 of the engine, a radiator 22, a thermostat device 23 having an additional function of a differential pressure valve, and a water pump 24 in this order; a heater circulation flow path 27 that circulates coolant from the cooling jacket 21 through a heater core 26 to the thermostat is device 23; and a bypass flow path 28 that directs coolant from the cooling jacket 21 to the thermostat device 23. In this configuration, the thermostat device 23 is controlled to adjust the degree of opening of the main circulation flow path 25 in accordance with the coolant temperature, while the heater circulation flow path 27 is always open, and the bypass flow path 28 is opened by its differential pressure valve function when the coolant pressure is increased due to an increase in the engine rpm during warm-up thereof. In FIG. 4, reference numeral 23 a denotes a temperature sensing part of the thermostat device 23, while 23 b denotes a differential pressure valve mechanism. The thermostat device 23 is a common, generally used thermostat, one specific example thereof being described, for example, in above Patent Literature 3 as thermostat 12 that has a similar configuration (although the configuration in which the heater circulation flow path 27 is maintained always open is not disclosed).

[Patent Literature 1] Japanese Utility Model Application Laid-Open No. Hei 3-127029

[Patent Literature 2] Japanese Patent Application Laid-Open No. 2000-289444 [Patent Literature 3] Japanese Patent Application Laid-Open No. 2007-120381 DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention

In the configuration shown in FIG. 4 or in the configuration described in Patent Literature 3, during warm-up when the coolant temperature is low, when the coolant pressure is increased due to an increase in the engine rpm, the differential pressure valve function of the thermostat device 23 is activated and the coolant is caused to flow through both the heater circulation flow path 27 and the bypass flow path 28, whereby the risk of trouble caused by an excessive coolant pressure is avoided. In the configuration shown in FIG. 4, however, the differential pressure valve mechanism 23 b that opens and closes the bypass flow path 28 is provided integrally with the thermostat device 23 which is disposed near the water pump 24. Therefore, the bypass flow path 28 is formed, as shown in FIG. 5, by disposing a duct 28 a forming the bypass flow path 28 separately from a duct 27 a forming the heater circulation flow path 27, such as to connect a flange 29 connected to a coolant exit of the cooling jacket 21 of the engine and the thermostat device 23. Therefore, two ducts 27 a and 28 a are required, because of which the number of components and the number of working steps are large, which leads to high cost and large weight, and makes the duct layout difficult to design. Another problem is that because the differential pressure valve mechanism 23 b is positioned near the water pump 24, it is susceptible to pulsation from the water pump 24, which reduces its durability.

In the configuration described in Patent Literature 3, too, the bypass flow path connecting a portion between the cooling jacket and the radiator of the main circulation flow path and the thermostat device is formed by a different duct from that of the heater circulation flow path, and further a control valve (differential pressure valve) is disposed in this bypass flow path. Therefore, the number of components and the number of working steps are large, because of which the cost is high and the weight is large, and also the duct layout is difficult to design.

In view of the above-described problems in the conventional techniques, it is an object of the present invention to provide an engine cooling device, which enables a reduction in the number of ducts for coolant circulation and a reduction in cost and weight as well as facilitation of the duct layout, and which improves durability of the differential pressure valve.

Means for Solving the Problems

The present invention resides in an engine cooling device, in which a coolant is circulated by a water pump through a coolant circulation flow path at least including a heater circulation flow path that circulates the coolant between a cooling jacket provided at least to one of a cylinder head and a cylinder block of the engine and a heater core, a bypass flow path that communicates the cooling jacket with a portion of the heater circulation flow path downstream of the heater core is provided, the bypass flow path being connected crosswise to a linear duct portion of the heater circulation flow path downstream of the heater core, and a differential pressure valve that opens when a fluid pressure on the side of the cooling jacket exceeds a predetermined value is disposed at a point of exit of the coolant from the cooling jacket to the bypass flow path.

With this configuration, the bypass flow path that bypasses the heater core is connected to a portion of the heater circulation flow path downstream of the heater core, and the heater circulation flow path is made to serve also as the flow path from this connecting portion to a thermostat device that is disposed near the water pump. Therefore, the duct forming the bypass flow path need not be extended as far as to the thermostat device and instead, only a single duct forming the heater circulation flow path need be disposed. Accordingly the number of components and the number of working steps can be reduced, which in turn reduces cost and weight, and also makes the duct layout easier to design. Moreover, the differential pressure valve that opens the bypass flow path when the fluid pressure on the side of the cooling jacket exceeds a predetermined value is disposed at the coolant exit of the cooling jacket, so that the flow path length from the water pump to the differential pressure valve is made long, because of which the differential pressure valve is less susceptible to pulsation of the water pump, whereby the durability of the differential pressure valve is improved. With the heater circulation flow path and bypass flow path being formed by a single duct, the duct diameter of the heater circulation flow path can be accordingly increased, as a result of which, the flow path resistance of the heater circulation flow path is reduced and thereby the heater performance can be improved.

With the bypass flow path being connected crosswise to the linear duct portion of the heater circulation flow path downstream of the heater core, the pressure pulsation from the water pump coming up the heater circulation flow path hardly enters the bypass flow path, whereby the durability of the differential pressure valve can be further enhanced.

EFFECTS OF THE INVENTION

According to the engine cooling device of the present invention, the bypass flow path is connected to the heater circulation flow path, and the heater circulation flow path is made to serve also as the flow path from this connecting portion to the thermostat device, and therefore only a single duct need be disposed. Accordingly the number of components and the number of working steps can be reduced, which in turn reduces cost and weight, and also makes the duct layout easier to design. Also, with the differential pressure valve that opens the bypass flow path being disposed at the coolant exit of the cooling jacket, the flow path length from the water pump to the differential pressure valve is made long, because of which the differential pressure valve is less susceptible to pulsation of the water pump, whereby the durability of the differential pressure valve is improved.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a configuration diagram of one embodiment of an engine cooling device of the present invention.

FIG. 2 is a perspective view showing a duct layout for forming a heater circulation flow path and a bypass flow path of the embodiment.

FIG. 3 includes diagrams for explaining circulation paths of the coolant in various operating states of the engine.

FIG. 4 is a configuration diagram of a conventional engine cooling device.

FIG. 5 is a perspective view showing a duct layout for forming a heater circulation flow path and a bypass flow path of the conventional example.

DESCRIPTION OF REFERENCE NUMERALS

-   -   1 cooling jacket     -   3 thermostat device     -   4 water pump     -   6 heater core     -   7 heater circulation flow path     -   7 b linear duct portion     -   8 bypass flow path     -   9 coolant circulation flow path     -   10 connecting portion     -   11 differential pressure valve

BEST MODE FOR CARRYING OUT THE INVENTION

One embodiment of the engine cooling device of the present invention will be hereinafter described with reference to FIG. 1 to FIG. 3.

In FIG. 1, the engine cooling device of the present embodiment includes: a main circulation flow path 5 connecting an engine cooling jacket 1, a radiator 2, a thermostat device 3, and a water pump 4 in this order; a heater circulation flow path 7 that passes a coolant from the cooling jacket 1 through a heater core 6 to the thermostat device 3; and a bypass flow path 8 that passes the coolant from the cooling jacket 1 such as to bypass the heater core 6. These main circulation flow path 5, heater circulation flow path 7, and bypass flow path 8 form a coolant circulation flow path 9.

The thermostat device 3 is configured to adjust the degree of opening of the main circulation flow path 5 in accordance with the coolant temperature and to pass the coolant to the radiator 2 in accordance with the temperature, so as to maintain the temperature of the coolant inside the cooling jacket 1 constant. Reference numeral 3 a denotes a temperature sensing part that senses the coolant temperature to adjust the valve opening degree. The heater circulation flow path 7 is configured to be always open.

The bypass flow path 8 is configured to connect the cooling jacket 1 with a portion of the heater circulation flow path 7 downstream of the heater core 6 so that coolant from the cooling jacket 1 bypasses the heater core 6 and flows back into the heater circulation flow path 7. More specifically, as shown in FIG. 2, a duct 8 a forming the bypass flow path 8 is connected crosswise to a linear duct portion 7 b of a duct 7 a forming the heater circulation flow path 7 downstream of the heater core 6. A connecting portion 10 of the duct 8 a to the linear duct portion 7 b of the heater circulation flow path 7 is disposed at a position near a point of exit of the coolant from the cooling jacket 1 to the bypass flow path 8, so that the bypass flow path 8 is formed relatively short.

A differential pressure valve 11 is disposed at the exit of the coolant from the cooling jacket 1 to the bypass flow path 8, which is opened when the pressure of the coolant in the cooling jacket 1 exceeds a predetermined value to let the coolant flow out into the bypass flow path 8. More specifically, as shown in FIG. 2, the differential pressure valve 11 is disposed such as to be built in a connecting flange 12 that connects the duct 8 a forming the bypass flow path 8 to the coolant exit of the cooling jacket 1.

In the above configuration, when the engine is in a warm-up state immediately after start-up, the temperature of the coolant inside the cooling jacket 1 is low, so that the main circulation flow path 5 is shut off at the thermostat device 3 and the coolant is not cooled in the radiator 2. In this state, while the engine is running at low to mid speeds (up to 4000 rpm), the coolant passes only through the heater circulation flow path 7 as indicated by a thick solid line in FIG. 3( a), circulating through the thermostat device 3 so that the vehicle interior is quickly warmed up.

In this warm-up state, when the engine runs at a high speed (4000 to 6000 rpm), a pressure buildup of the coolant inside the cooling jacket 1 opens the differential pressure valve 11, whereby, as indicated by a thick solid line in FIG. 3( b), while the coolant 1 keeps passing through the heater circulation flow path 7, an excess amount of coolant for the heater core 6 is passed through the bypass flow path 8. The excess coolant then joins the coolant passing through the heater circulation flow path 7 at the connecting portion 10 between the bypass flow path 8 and the heater circulation flow path 7, after which it flows through the heater circulation flow path 7 toward the thermostat device 3. Since the coolant that has passed through the bypass flow path 8 joins the coolant passing through the heater circulation flow path 7 as described above, the duct 7 a forming the heater circulation flow path 7 employed in the present embodiment is wider in diameter than the duct in the conventional heater circulation flow path. To give a specific example, when the bypass flow path 8 has an inside diameter of 8 mm, the inside diameter of the heater circulation flow path 7 of the present embodiment is set 16.6 mm as compared to the conventional heater circulation flow path 27 having an inside diameter of 14.6 mm.

As the temperature of the coolant inside the cooling jacket 1 rises, the main circulation flow path 5 is opened at the thermostat device 3, so that the coolant inside the cooling jacket 1 circulates mostly passing through the main circulation flow path 5 and the heater circulation flow path 7 as indicated by a thick solid line in FIG. 3( c). In this state, normally, the pressure of the coolant inside the cooling jacket 1 is not high, so the differential pressure valve 11 remains closed and the coolant does not flow into the bypass flow path 8. Even in this state, however, when the flow rate of the coolant flowing through the main circulation flow path 5 is largely reduced at the thermostat device 3 so that the flow rate of the coolant flowing into the heater circulation flow path 7 is reduced, if the engine is operated at a high rpm, the pressure of the coolant inside the cooling jacket 1 is increased and the differential pressure valve 11 is opened, so that the coolant circulates through the bypass flow path 8.

According to the engine cooling device of the present embodiment described above, the bypass flow path 8 that bypasses the heater core 6 is connected to a portion of the heater circulation flow path 7 downstream of the heater core 6, and the heater circulation flow path 7 is made to serve also as the flow path from this connecting portion 10 to the thermostat device 3 disposed near the water pump 4. Therefore the duct 8 a forming the bypass flow path 8 need not be extended as far as to the thermostat device 3 and instead, only a single duct 7 a forming the heater circulation flow path 7 need be disposed. Accordingly the number of components and the number of working steps can be reduced, which in turn reduces cost and weight, and makes the duct layout easier to design.

The differential pressure valve 11 that opens the bypass flow path 8 when the fluid pressure on the side of the cooling jacket 1 exceeds a predetermined value is disposed at the coolant exit of the cooling jacket 1, so that the flow path length from the water pump 4 to the differential pressure valve 11 is made long. Because of this fact, the differential pressure valve 11 is less susceptible to pulsation of the water pump 4, whereby the durability of the differential pressure valve 11 is improved. In particular, with the duct 8 a forming the bypass flow path 8 being connected crosswise to the linear duct portion 7 b of the heater circulation flow path 7 downstream of the heater core 6, the pressure pulsation from the water pump 4 coming up the heater circulation flow path 7 hardly enters the bypass flow path 8, and the differential pressure valve 11 disposed at the starting end thereof is unlikely to be affected and so the durability of the differential pressure valve 11 can be further enhanced.

With the heater circulation flow path 7 serving also as the bypass flow path 8, and the single duct 7 a forming the heater circulation flow path 7 also forming the bypass flow path 8, the diameter of the duct 7 a for the heater circulation flow path 7 is accordingly increased, as a result of which, when the coolant is not passing the bypass flow path 8, the flow path resistance of the heater circulation flow path 7 is low. Accordingly, an effect of improving the heater performance is also achieved.

INDUSTRIAL APPLICABILITY

According to the engine cooling device of the present invention, the bypass flow path is connected to the heater circulation flow path, and the heater circulation flow path is made to serve also as the flow path from this connecting portion to the thermostat device. Therefore, only a single duct need be disposed, whereby the number of components and the number of working steps are reduced, which in turn reduces cost and weight, and also makes the duct layout easier to design. Moreover, the differential pressure valve that opens the bypass flow path is disposed at the coolant exit of the cooling jacket, so that the flow path length from the water pump to the differential pressure valve is made long. Because of this fact, the differential pressure valve is less susceptible to pulsation of the water pump, whereby the durability of the differential pressure valve is improved. Thus the present invention can be advantageously used for engine cooling devices. 

1. An engine cooling device, comprising: a coolant circulation flow path at least including a heater circulation flow path that circulates a coolant between a cooling jacket provided at least to one of a cylinder head and a cylinder block of an engine and a heater core; a water pump; and a coolant that is circulated by the water pump through the coolant circulation flow path, wherein the engine cooling device further comprises: a bypass flow path that communicates the cooling jacket with a portion of the heater circulation flow path downstream of the heater core; and a differential pressure valve that opens when a fluid pressure on the side of the cooling jacket exceeds a predetermined value and that is disposed at a point of exit of the coolant from the cooling jacket to the bypass flow path.
 2. The engine cooling device according to claim 1, wherein the bypass flow path is connected crosswise to a linear duct portion of the heater circulation flow path downstream of the heater core. 